Switch



Sept. 22, 1942. v, EBER 2,296,374

SWITCH Filed May 14, 1940 m VICTOR WEBER.

ATTORNE".

Patented Seph22, 1942 2,290,374 swrron Victor Weber, Greensburg, Pa., assignor to Robertshaw Thermostat Company, Youngwood, Pa., a corporation of Pennsylvania Application May 14,

14 Claims.

This invention relates to electric switches and more particularly to thermostatically operated electric switches for temperature control.

The invention is particularly applicable, although not limited to the regulation of temperature in ovens, surface heaters or other compartments of electric ranges or other appliances where automatic control of temperature is desired. The automatic control of temperature in such devices is conveniently performed through the medium of a liquid filled container subjected to the temperature of the oven or, other chamber and operatively connected to an expansible and contractible element which opens andmloses an electric switch at predetermined temperatures. It is generally desirable that the switch and its operating element be located at a remote position out of heating range of the heating device and at a point where the temperature at which the switch will make and break an electric circuit may be manually controlled.

It is an object of this invention to improve the means of making and breaking an electric circuit thermostatically,

Another object of they invention is to render the device responsive at any desired temperature within operating limits.

Another object of the invention is to assure positive make and break in the circuit periodically in response to temperature changes at the point being controlled.

- Another object of the invention is to render the device sensitive'and operable under temperature changes causing relatively small movements of an expansible and contractibleelement.

Another object of the invention is to construct the switch device with a minimum number of parts adapted to economical manufacture and eflicient operation.

7 in Fig. 1 but with parts removed;

' Fig. 3 is a sectional view taken on the line Ill-Ill looking in the direction indicated by the arrows;

Fig. 4 is a partial schematic view showing the switching mechanism in one position; and

Fig. 5 is a view similar to Fig. 4 but showing the parts in another position.

Referring more particularly to Figs. 1-3 inelusive of the drawing there is provided a housing ll of suitable insulating material and of a hollow substantially rectangular shape open at both ends. A cover plate I! extends across one 1940, Serial No. 335,055

open end of the housing I and another cover plate I4 forms a closure for the opposite open end. These cover plates l2 and I4 are secured in position by screws I6 projecting through the cover l2 and through holes ill in the walls of the housing llland threadedly engagin raised portions or bosses 20 formed on the cover plate l4,

Projecting through an aperture 22 centrally disposed in the cover I4 is a hollow connection 24 to which, in this embodiment, the outer end of the flexible tube 26 of a thermostat bulb 28 is secured. The connection 24 may be suitably threaded, as shown, for engagement with a nut 30 externally of the housing I0 and serving to draw a collar 32 on the connection 24 securely against the inner face of the cover H for retaining the connection 24 in position. A head portion 34 on the connection 24 forms an abutment for the inner member of an expansible and contractible diaphragm element 36, the inner member being provided with the usual axial perforation permitting communication between V the hollow connection and the interior of the diaphragm element. The outer member of the diaphragm 36 carries a projecting button 36 having a reduced rounded end 39. Preferably, the diaphragm element 36 which is of the usual cupshaped form wholly encloses the collar 32 and head 34 of the connection 24, such construction being permitted by the provision of a depressed portion 40 on that part of the cover l4 carrying the connection 24. The thermostatic bulb 28, capillary tube 26 and diaphragm element 36 are filled with. suitable thermally expansible fluid which serves to expand and contract the diaphragm element upon temperature changes in a well-known manner.

The cover l2 on the opposite end of the hous- 4.0 ing I 0 is provided with an aperture 42 which, while being located in the same longitudinal plane as the aperture 22 in cover I 4, is radially ofiset from the axis thereof. -A nut 44 is secured in the aperture 42 as by peening the inner end 46 thereof against the inner face of the cover, this operation serving also to retain one end of a bracket 48 firmly against the outer face of the cover l2. Threadedly engaging the nut 44 is an adjusting screw 50 having a reduced rounded end portion 52 at one end projecting into .the hollow housing and a shank portion 54 at the other end. The shank portion 64 is split for a portion of its length for resilient engagement with an operating handle 66 whereby the adjusting screw may be rotated in the nut 44.

The bracket 48 is designed to aflord means of mounting the switch device in association with an oven or other compartment of an electric stove or other structure, the temperature of which the switch is adapted to control, Hence,

other structure. As is customary in such devices the handle may carry indicia cooperating with a station on the panel for the various temperatures to which the device may be set.

Suitable means for calibration and limiting rotation of the handle may be provided, such as a plate 99 rotatable on the shank 59 and having an arm 58 projecting into a complemental' slot formed in the body of the handle 56. A second arm It located diametrically opposite the arm 98 I on the plate 56 is adapted to engage a projection 72 formed on the panel 62 and extending into the opening 6-9 for limiting rotation of the handie. The plate 96 may further be provided with a pair of arcuate slots It adapted to receiv a portion of a screw it which projects from a looking plate is journaled on the shank 5 3. As is apparent, the screw it may be loosened to permit arcuate movement of the plate 66 to locate any desired indicia on handle 56 with reference to the station on the panel, whereupon screw I6 may again be tightened to retain such adjustment. Such calibration is well-known and further description is deemed unnecessary.

This invention more particularly contemplates improvements in the switch operating mechanism whereby an electric circuit may be made and broken at desired operating temperatures. To this end, one wall of the housing I0 is provided in this instance with a pair of spaced recesses 80 extending from the end face carrying the cover plate I2 to a point midway of the other end face. The bottoms 32 of these recesses are preferably formed at an angle to the plane of the end faces of the housing I0 whereby a pair of switch arms 84 secured as by the screws 86 to the bottoms 82 project obliquely into th housing I0. The inner ends of the switch arms 89 carry contacts 88 and the outer ends are provided with terminals 90 which may be connected to a source of electric current.

The wall of the housing I0 opposite that having the recesses 80 is also provided with a pair of recesses 92, the bottoms of which, however, are substantially parallel with the end faces of the housing I0. These recesses 92 are slightly less in depth than the recesse 00 in order that switch arms 94 which engage the bottoms of said recesses 92 and project into the housing may overlie the switch arms 84. A pair of separate terminals 96 which project from the housing I0 are retained in contact with the switch arms 94 by screws 98; these screws 98 also serving to secure both switch arms 94 and terminals 96 in the recesses 92 in the housing. The terminals 96 may be connected to the heating unit of the surface heater or other device for which control is desired.

The switch arms 94 are preferably formed of springy material, such as phosphor bronze, relatively thin compared with switch arms 84, and carry contacts I00 adapted to engage .the contacts 88 on switch arms 84. The parts are so arranged that when assembled as so far described, the switch arms 94 will be under tension biased toward the switch arms 84 for a purpose to be described hereinafter.

Mounted in the housing I0 is an operating lever I02 preferably formed of insulating material, such'as Bakelite. The main body portion of the lever I02 is substantially in the form of a triangle with the base thereof positioned ad.- jacent to the contacts 88 and I00. A raised knife-edge bearing portion I08 extends across the face of the lever I02 at the base thereof and is adapted to contact with the switch arms 99 in proximate relation with the contacts I00 associated therewith. The end of the main body portion of lever I02 forming the apex of the triangle is made thinner in cross-section than the base portion in order not to interfer with tilting of the lever IIlZtoward the switch arms 94%.

Extending from the apex of the triangular body portion of lever I02 to a point adjacent the knife-edge bearing I08 i a raised portion Ho which is narrow enough in width to project. be-

tween the pair of switch arms 99 and provide clearance therefor. A depression I04 having a conical bottom is formed in the raised portion H0 and is adapted to receive the rounded end portion 52 of the adjusting screw 50. The wall of the depression I09 is spaced from the rounded end. 52 which normally engages with the conical bottom portion only and forms a pivot point for the lever I03.

The face of t e lever I02 opposit that having the raised portion is also provided with a depression I06. This depression, however, is located in the central portion of the triangular body and may be wholly conical in form and is adapted to receive the rounded end portion 39 0f the button 38. As in the case of the depression I09, the diverging sides of the wall of conical depression I09 likewise provide clearance for the button 38 and the rounded end 39 forms a second pivot point for the lever I02. The depressions I09 and I06 are located relative to each other along the same longitudinal plane as in the case of the pivot points 52 and 38.

The operating lever I02 is thus capable of being supported in housing I0 by engagement with the rounded ends 39 and 52 and the free ends of switch arms 94. As the two switch arms 94 act substantially a a unit the engagement of their free ends may be considered for the purpose of simplicity in description as forming a single pivot point for the lever I02 in addition to the two separate pivotpoints provided by the rounded ends 39 and 52. Thus, in making'and breaking the circuit through the switch either thermostatically or manually, the three pivot points are each utilised as such while each is adapted to perforni someother function. For example, rounded end' 39 serves not only as a pivot point for le'ver I02 when the adjusting screw 50 is operated to manually open the switch, but also serves as an operating member when thermostatic control of the switch occurs.

It will thus be apparent that as none of the three pivot points is fixed with respect to the engagement of the lever with the rounded end 39. Now, if 'the diaphragm expands and moves rounded end 39 further into the housing the lever will have some pivotal movement on its knifeedge I08 around a point on the switch arm, but I at the same time this pivot point is not fixed and some slippage will probably occur. The lever will finally be engaged closely between both the rounded ends 39 and 52 as well as by the free ends of the switch arms 94 providing sufficient movement of the diaphragm occurs. Hereinafter, the pivotal movement of the lever is defined as such, while the other motion or slippage is defined as a bodily shift to distinguish.

, When the operating handle 56 is first turned to a low temperature position and the bulb 2815 at room temperature, the switch parts will be substantially in the position shown in Fig. l. The operating handle may then be rotated to any desired setting of the indicia thereon which will serve to withdraw the adjusting screw 50 slightly outwardly of the housing I0. The lever I02 is then supported more loosely on the two pivot points 39 and 52 and a larger amount of expansion of the diaphragm 36 will be required to move it to operate switch arm 94 to break the circuit. Such operation will occur whenever the temperature at the bulb reaches that for which the handle is set, assuming that proper calibration has been made by the means provided. The movement of the lever I02 due to the engagement of the rounded end 39 with the depression bottom I06 causes the pivotal movement and bodily shift of the lever I02 previously described over toward the rounded end 52 of the adjusting screw 50 until a pivoting action commences around that point. Such action will cause the knife-edge I08 to move the free end of switch arms 94 away from the arms 84 and thus separate contacts 88 and I00. The circuit through the switch will remain broken until the temperature at the bulb again drops and causes contraction of the diaphragm with consequent reverse movement of the knife-edge I08. The bias of the switch arms 94 tending to cause movement toward switch arms 84 also causes the free ends thereof to follow reverse movement of the knifeedge I08 until the respective contacts engage. Reference may be had to Fig. 5 of the drawing showing in an exaggerated manner the position of the lever I02 when the circuit is broken by thermostatic control at high heat position of the handle 58. I

When it is desired to disconnect the electric heating device from the source of current supply, the handle 56 may be rotated to the off position customarily provided. Such movement, which will be in reverse direction to that for the on and heating positions, will serve to project the adjusting screw inwardly of the housing I0. The lever I02 will tilt around the button 38 as a pivot point and the knife-edge I08 will move the contacts 88 and I00 apart as previously described. Reference may be had to Fig. 4 of the drawing for a diagrammatic view of the parts in exaggerated position when such manual control is applied.

From the foregoing description it will be apparent that positive control of the temperature in a heating device has been provided which will operate at any desired temperature within operating limits. The lever construction renders the device sensitive to small movements of the diaphragm element which are multiplied thereby to make and break the circuit positively. There are no springs or other devices to complicate the switch mechanism which is compact and easily accessible for assembly and adjustment. While this embodiment of the invention shows and describes a double pole switch it will be understood that more or less contacts may be provided and other details of construction may be changed or modified without departing from the spirit of the invention which generally consists in a device capable of carrying out the objects set forth and in the novel parts and combination disclosed and defined in the appended claims.

I claim:

1. In a switch, an operating lever adapted for pivotal movement and bodily shift, a thermally actuable member having means for supporting said lever and transmitting said pivotal movement and bodily shift thereto in response to temperature changes, a switch arm movable by said lever to open and close the switch, and manually actuable means upon which said lever may pivot to operate the switch in response to movements of the thermally actuable member, said means being adjustable toward and away from the lever to vary the amount of bodily shift of said lever before pivoting occurs, thereby effecting operation of the switch at predetermined temperatures.

2. In a switch, an operating lever adapted for pivotal movement, a thermally actuable member having means for supporting said lever, a manually actuable member having means for supporting said lever, at least one of said members being adapted to transmit pivotal movement to said lever, and a switch arm upon which said lever may pivot when such movement occurs.

3. In a switch, a thermally actuable member movable in response to temperature changes, a manually actuable member movable independently of said thermally actuable member to set the desired operating temperature, an operating lever adapted for pivotal movement upon either of said members, and adjustable by movement of one of said members substantially parallel to the other, and contacts associated with said lever and operable to be opened and closed by pivotal movement. thereof.

4. In a switch, an operating lever adapted for pivotal movement, a thermally actuable member having means for supporting said lever, a manually actuable member having means for supporting said lever, said lever being adapted to pivot on one of said members in response to movements of the other, and a switch arm forming an additional means upon which said lever may pivot when said movements occur.

5. In a switch, an operating lever adapted for pivotal movement, a thermally actuable member having means for supporting said -lever and transmitting pivotal movement thereto in response to temperature changes, a manually actuable member having means for supporting said lever and transmitting pivotal movement thereto, said lever being adapted to pivot on one of said members in response to movements of the other, and a switch arm forming an additional means upon which said lever may pivot when said movements occur.

6. In a switch, a thermally actuable member movable in response to temperature changes, a manually actuable member movable independently of said thermally to actuable member to set the desired operating temperature an operating lever adapted for pivotal movement upon either of said members and adjustable by movement of one of said members substantially parallel to the other, a fixed contact, and a movable contact biased toward said fixed contact and operable to be moved away therefrom by pivotal movement of the lever.

'7. In a switch, a thermallyactuable member movable in response to temperature changes, a manually actuable member movable independently of said thermally actuable member to set the desired operating temperature, anoperating lever supported between said members for'pivotal movement thereon, said members both functioning alternately as pivots for the lever and as operating members therefor capable of moving the lever upon manual or thermal actuation of when moved by the other, the movements of said members being substantially parallel to each other, and a switch arm operable by said lever to open and close the switch either by movement of said thermally actuable member in response to temperature changes or by movement of the manually actuable member independently thereof.

9. In a switch, a housing, an expansible and contractible element/mounted in said housing, a projection on said element movabletherewith upon expansion and contraction, an adjusting member mounted in the housing opposite said element but radially offset therefrom, a fixed contact in said housing, a movable switch arm carrying a contact and biased towards closed contact position, and an operating lever adapted to be suspended on said projection and member, said lever being engaged by said switch arm in radially offset relation to said projection but remote from said adjusting member, whereby said lever is maintained in operative relation with said projection and member solely by said movable switch arm.

10. In a switch, a thermally actuable member movable in response to temperature changes, a

manually actuable member movable from a direction opposed to said thermally actuable member, each of said members having pivot points thereon, an operating lever supported from opposite sides by said pivot points and adapted to both pivot and shift bodily with respect to said members in'response to movements thereof, said members functioning alternately as pivots and as operating members therefor capable. of moving the lever upon manual or thermal actuation of said members, fixed and movable contacts, and a resilient switch arm for said movable contact adapted to bias said lever by pivotal or bodily movement thereof to keep the contacts closed but being operable by pivotal movement of the lever v to open contact position.

11. In a switch, a thermally actuable member movable in response to temperature changes, a manually actuable member movable from a direction substantially parallel and axially opposed to said thermally actuable member, each ofsaid members having pivot points thereon spaced one from the other in substantially the same'longitudinal plane, an operating lever supported from opposite sides by said pivot points and adapted to both pivot and shift bodily with respect to said I members in response to movements thereof, said members functioning alternately as pivots and operating members for the lever, a fixedcontact extending adjacent the lever, a movable contact engageable with said fixed contact, and a switch arm for said movable contact resiliently maintaining engagement with said lever to bias it by pivotal or bodily movement thereof to keep the contacts closed butv being operable by pivotal movement of the lever to open contact position.

12. In a switch, a housing, an expansible and contractible element mounted in said housing, f

means responsive to. temperature changes operatively connected to said element for causing expansion and contraction thereof, a projection on said element movable therewith upon said expansion and contraction, an adjusting member mounted in the housing opposite said element but radially offset therefrom, an operating lever having depressions therein for said projection and member and supported in the housing thereby, said lever being adapted for pivotal movement on points established by either said projection or said member and to shift bodily therebetween, a pair of fixed contacts carried by said housing, and a pair of flexible switch arms carrying contacts and adapted to engage said lever at spaced points forming triangular relation with one of said pivot points, said switch arms being adapted to bias said lever by pivotal or bodily movement thereof to keep the contacts closed but being operable by pivotal movement of the lever to open contact position.

13. In' a switch, a housing, an expansible and contractible element mounted in said housing, means responsive to temperature changes operatively connected to said element for causing expansion and contraction thereof, a projection on said element movable therewith upon said expansion and contraction, an adjusting member mounted in the housing opposite said element but radially ofiset therefrom, an operating lever having substantially conical depressions therein for said projection and member and supported in the housing thereby, said lever being adapted for pivotal movement on either said projection or member and to shift bodily therebetween, a knife-edge projection on one end of said lever, a pair of fixed contacts carried by said housing adjacent said knife-edge projection, and a pair of flexible switch arms carrying contacts and adapted to engage said knife-edge projection to bias the lever by pivotal or bodily movement thereof to keep the contacts closed but being operable by pivotal movement of the lever to open contact position.

14. In a switch, a thermally actuable member movable in response to temperature changes, a manually actuable member movable from a direction opposed to said thermally actuable member, each of said members having pivot points thereon spaced one from the other in substantially thesame longitudinal plane, an operating member adapted to move on said pivot points in response to movements of said members, a pair of fixed: contacts adjacent said lever, and a pair of switch arms carrying contacts and adapted to engage said leverat spaced points forming triangular relation to one of said pivot points and enclosing the other therewithin, said switch arms biasing said lever to keep said contacts closed but being operable upon-movement of the lever to open contact position.

VICTOR WEBER. 

